In a case where a device performs communications with another device, there is often a problem with the quality of the network that connects those devices. In this specification, “the quality of a network” represents a throughput as an effective speed, the amount of packet loss in transmitted packets, a packet loss rate, a delay time caused in transmission, a jitter as a variation of the time required for a packet arrival, a RTT (Round Trip Time) as the time required for a packet traveling back and forth between a communication terminal and another communication terminal, or a packet delay distribution.
There have been suggestions for network quality measurement. The first one of the conventional suggestions involves a passive-type measuring operation in which packets flowing through a network are captured, and the traffic of the flowing packets is measured (see Non-Patent Document 1, for example).
The second one of the conventional suggestions involves an active-type measuring operation in which test packets are transmitted through a network, so as to measure the packet loss rate of the network (see Non-Patent Document 2, for example).
[Non-Patent Document 1] Kiminori Sugauchi, Hidemitsu Higuchi, Kazuaki Tsuchiya, and Jun Mizuno, “Traffic Monitoring Technique for High Traffic Networks”, Technical Report of IEICE, NS2003-312, IN2003-267 (2004-03), March 2004 [Non-Patent Document 2] Masato Tsuru, Shuji Uetsuki, Yoshiaki Kitaguchi, Shinichi Nakagawa, Yuji Oie, “Experiments in Estimating Internal Packet Loss Rate Based on End-to-End Measurement”, Technical Report of IEICE, NS2001-226 (2002-03), March 2002